The present invention relates to devices for extracting useful energy from fluent media, and more particularly, it relates to improved apparatus embodying lift foil elements with economical power takeoff means.
As taught in Bailey, U.S. Pat. No. 3,978,345, various devices have been proposed for utilizing the energy contained in fluent media. Some of the more common fluent media containing kinetic energy are fresh water, sea water, and the planetary atmosphere. The kinetic energy in water is contained in currents, such as river currents, tidal currents, and the like; the energy of the atmosphere, in the movement commonly referred to as the wind.
The use of potential energy from moving streams of water, such as at falls or natural or artificial dams, has long been known and has been used historically for the operation of various mills and more recently for the generation of electrical power. The difficulty with such sources of potential energy is that the potential energy is available only at a relatively small number of sites, namely, at natural falls or at dams. Accordingly, such possible sources of energy cannot be utilized in many parts of the world, such as in deserts or at sea level.
Another hallmark of such classical systems for the utilization of potential energy in a liquid medium such as water is that the flow is required to be unidirectional, and it is ordinarily impracticable to use such devices where the flow is multidirectional. Such multidirectional flow occurs in tidal current schemes which have been proposed, but due to limitations of apparatus and the requirement for efficiency in use, even such schemes for harnessing tidal currents generally involve power generation only by unidirectional flow, that is, by permitting the water to flow inshore, trapping it in a basin, and then releasing it through an appropriate energy conversion device when the tidal level of the water is lower than the level of the water captured in the basin.
The power in the wind has in the past been chiefly used to drive devices rotating on a horizontal axis, such as propellers, windmills, and turbines. The use of various devices rotating on a vertical axis such as Darrieus machines and Savonius cylinders is also known.
Such machines can be effective, but they generally define a relatively small area in which the wind can act on them. Moreover, they generally take up valuable space on land, which space could be used for agricultural, residential, or industrial purposes.
The above-mentioned Bailey patent describes a vastly improved system for harnessing energy. The Bailey system can be used virtually anywhere that supports can be provided, and it is simple in construction, easy to maintain, and relatively efficient. It is well suited to the need for extracting kinetic energy over a large sectional area of a fluent medium, as is required with relatively diffuse media.